Macroinvertebrate diversity indices: A quantitative bioassessment of ecological health status of an oxbow lake in Eastern India

Aquatic macroinvertebrates, which play a significant role in the food chain of an ecosystem, are used in fresh water quality assessment to identify the environmental stress resulting from a variety of anthropogenic disturbances. Seasonal surveys of macroinvertebrate communities were conducted from April 2013 to March 2014 in Chhariganga oxbow lake of Nadia District of West Bengal, an eastern state of India. In order to bioassess water quality and aquatic health analysis using diversity indices, viz. Shannon-Wiener and Simpson’s diversity index, species richness and evenness, and total abundance with composition trends were carried out. Taxon richness values of 14, 14, and 18, evenness values of 0.80, 0.71, and 0.73, Shannon-Wiener Index values of 2.10, 1.88, and 2.12, and Simpson’s index values of 0.15, 0.22, and 0.20 were determined for macroinvertebrates found during pre-monsoon, monsoon, and post-monsoon period, respectively. In the present study, low diversity indices, like the Shannon-Wiener Index, demonstrated clearly that the selected lake is polluted and has high anthropogenic activity which has rendered the lake bad to poor health status especially during monsoon season. Therefore, it is necessary to regulate and prevent the jute retting process, and its intensity and density during the monsoon to enhance biodiversity in order to ensure sustainable management and conservation of aquatic environment of the oxbow lake.